Hard Disk Drives Overview

Hard Disk Drives

• Hard disk drives (HDDs) are the primary storage devices in most modern computers.
• HDDs store data for the computer system, including applications and operating systems.
• Early HDDs were slow and unreliable, but advancements have made them much faster and more reliable.

Hard Drive Advancements

• Storage capacity: Originally 5MB, now up to 8TB+.
• Data transfer rates: Originally 85KBps, now 150MBps+.
• Access time: Originally around 85ms, now 10-20ms.
• Cost: Originally $2,000 for 10MB, now well under $100 for 1TB.

Inside a Hard Drive

• Components: Platters, read/write heads, actuator arms, motors, air filters.
• Platters: Made from aluminum or ceramic composite material; rugged and solid; store data. They are lightweight and have low thermal expansion.
• Air Filters: Recirculating filter, and barometric filter. The recirculating filter filters small particles while the barometric filter provides ventilation for pressure equalization.

Care of a Hard Disk Drive

• Extreme temperatures: Avoid exposing HDDs to extreme temperatures, such as those found in a car trunk.
• Safe operating temperatures: If exposed to extreme temperatures, wait until the HDD reaches safe operational temperature before powering it on.

Read/Write Heads

• Coated platters: Both sides of the platter are coated with magnetic surfaces for data storage.
• Two heads: Each platter needs two read/write heads, one for each side.
• Air cushion: The heads float on a thin air cushion, never making contact with the platter surface during operation.
• Extremely small air buffer: The air buffer space between the read/write head and the platter is very small, measured in millionths of inches.

Actuator Arm

• Read/write head location: Read/write heads are located on the actuator arm's tip.
• Voice coil motor: In modern HDDs, the actuator arm is positioned by a voice coil motor.

Spindle

• Multiple platters: HDDs have multiple platters, separated by spacers and held together.
• Rotation: The spindle and platters rotate at a constant speed.

Voice Coil Motor

• Linear motor or voice coil: Current HDDs utilize this technology to move the actuator arm
• Magnetic field: Electrical current generates a magnetic field that moves the actuator arm.
• Improved performance: Significantly faster, more accurate, and more reliable than stepper motors.
• Automatic parking: Hard drive heads automatically park when not in use.

Full Speed Ahead

• RPM rates: Most HDDs spin at either 5,400 or 7,200 RPM.
• High Performance: High-performance HDDs spin at 10,000 RPM or higher; some models up to 15,000 RPM.

Hard Drive Assembly

• Clean rooms: HDDs are assembled in sealed clean rooms under sanitary conditions.
• Dust sensitivity: A tiny speck of dust can cause a hard drive head crash.
• Repair limitations: Few companies have the capacity for HDD repair due to complexity and expense.
• Replacement: Malfunctioning HDDs are typically replaced.

Hard Drive Organization

• Tracks: Concentric circles on the platter; thousands per platter.
• Cylinders: Tracks of the same diameter on all platters are a cylinder.
• Sectors: Sections of a track; smallest allocatable unit. Old HDDs typically held 512 bytes per sector; modern HDD uses 4KB.
• Clusters: Groups of sectors; the smallest unit of space that can be used for a read/write operation.

Logical Block Addressing (LBA)

• Modern method: Using logical block addressing (LBA), each sector on a HDD is assigned a unique identifier.
• Older addressing: Older computers used 28-bit addressing which limited maximum storage to 137GB.
• Modern addressing: Current systems use 48-bit addressing, allowing HDDs up to 144PB.

Hard Drive Interfaces

• Interfaces: Three major interfaces exist: Serial ATA (SATA), Parallel ATA (PATA) and Small Computer System Interface (SCSI).
• SATA: 7 pin data connector
• PATA: 40 pin data connector
• SCSI: Variety of connectors; typically used in servers

Capacity Confusion

• GB calculation: Some HDD manufacturers calculate capacity in gigabytes by dividing by 1000 (rather than 1024).
• Advertised vs. formatted: This results in an advertised capacity that's noticeably higher than the operating system's reported capacity.

Head Crash

• Contact damage: A head crash occurs when a read/write head touches a rotating platter.
• Data loss: This results in permanent damage to the magnetic media on the hard drive's platter, leading to data loss.
• Causes: A head crash can occur due to dirt, or too much shock or vibration.

SMART

• Self-Monitoring Analysis and Reporting Technology (SMART): An interface for monitoring hard drive performance and condition.

• Predictive maintenance: SMART allows for the predictive maintenance.

• Data backup: Vital information can alert users to impending failure, allowing ample time to back up data.

• Diagnostics: Provides information on aspects of the internal operation of a hard drive such as internal temperature, Power-on hours, spin-up retry count, Power cycle count, Seek error count, and Throughput performance.

• Software required: Software is required to collect and display SMART data. Freeware/Shareware software solutions are available, alongside commercially available programs.

This quiz delves into hard disk drives, exploring their historical evolution, advancements in storage capacity, data transfer rates, and access times. Additionally, it covers the various components that make up a hard drive, providing a comprehensive understanding of its functionality and importance in modern computing.